Air pollution, specifically diesel exhaust (DE), is associated with the top four causes of mortality in the United States: heart disease, cancer, stroke, and chronic lower respiratory diseases. In spite of the prevalence of these conditions and magnitude of DE exposure in ambient urban and occupational environments, few biologically based attempts have been made to thwart the effects of acute or chronic exposures. Oxidative stress is a prevailing theory in the mechanism of action of air pollutant-induced adverse health effects. Antioxidants, the body's defense against oxidative stress, are commonly employed by CAM practitioners to prevent and reduce the adverse consequences of exposure to pollutants. This research application is intended to examine a CAM product (glutathione (GSH)) and model (prevention) in an attempt to reduce oxidative stress induced by DE exposure. The UW exposure laboratory offers an unparalleled opportunity to examine CAM interventions in augmenting human responses to DE. This nested research application is a double-blind, placebo-controlled, cross-over experiment to determine if inhaled GSH can blunt the observed oxidative stress associated with controlled DE exposure. While biologically based, scientifically plausible, and currently used in the CAM community, this promising intervention lacks exposure-specific evidence. The long-term objective of this research is to rigorously examine potential CAM interventions in augmenting adverse health effects induced by pollutants that pose a substantial ongoing public health burden.